Process for recovering molybdenum values from molybdenite ore materials

ABSTRACT

AN IMPROVEMENT IN THE PROCESSING OF MOLYBDENITE ORE MATERIALS, USUALLY MOLYBDENITE-BEARING COPPER SULFIDE CONCENTRATES, FOR THE RECOVERY OF THE MOLYBDENUM VALUES CONTAINED THEREIN. INSTEAD OF THE CONVENTIONAL FLOTATION CIRCUIT, WHEREIN MIDDLINGS ARE RECIRCULATED AND MOLYBDENITE VALUES THEREIN RECOVERED IN A RELATIVELY HIGH GRADE MOLYBDENITE CONCENTRATE AS A FINAL PRODUCT MEETING ESTABLISHED SPECIFICATIONS AS TO MOS2 CONTENT, AND NORMALLY ALSO AS TO CHEMICAL GRADE, AT LEAST A PART OF THE MIDDLINGS ARE DRAWN OFF AS A RELATIVELY LOW GRADE MOLYBDENITE INTERMEDIATE PRODUCT AND ARE TREATED SEPARATELY FOR THE RECOVERY OF THE CONTAINED MOLYBDENUM VALUES. RECOVERY OF MOLYBDENUM VALUES IN TERMS OF BOTH HIGH GRADE CONCENTRATE AND THE LOW GRADE INTERMEDIATE PRODUCT IS SIGNIFICANTLY HIGHER THAN IS RECOVERY OF MOLYBDENUM VALUES IN TERMS OF THE CONVENTIONAL HIGH GRADE CONCENTRATE BASED ON THE CUSTOMARY RECIRCULATION OF MIDDLINGS.

Sept. 10, 1974 SPEDDEN ETAL 3,834,894

PROCESS FOR RECOVERING IOLYBDENUK VALUES FROM MOLYBDENITE ORE MATERIALS Filed April 10. 1969 2 Sheets-Sheet l {PR/0R ART) UPGRADED COPPER SULFIDE-MOLYBDENITE FLOTATION CONCENTRATE (8.8l Cu 8.0|% M082) [M082 CLEANER FLOTATION Noll SINK FLOAT llRlMARY HEAT TREATMEN?! COOL-+ -WATER EM w E [@NGUE ROUGHER M] LSECONDARY HEAT TREATMEN7| FLOAT ELK COOL- WATER @ANODE CLEANER FLOTATION| GANGUE FLOTATlON 51 FLOAT 's 1' FLOAT (GANGUE CLE E R rfiOglCENTRATE o 2 Mos CLEANER 0.22 /o RECOVERED M082) FLOTATION No 2 M052 ROUGHER FLOTATION TAILING O.6| Mos 7.88% RECOVERED M082 INVENTORS HENRY RUSH SPEDDEN Y ARTHUR WT LAST ATTORNEYS SINK FLOAT SINK FLOAT M82 SCAVENGER FLOTATIOW] M082 CLEANER FLOTATION No 3 i ii FLOAT SILIK FLOAT- M082 SCAVENGER TAILING HIGH-GRADE 0.66 M06 M082 CONCENTRATE 7.66% RECOVERED M082 89.26% M082 92.12% RECOVERED M082 Sept. 10, 1974 H. R. SPEDDEN L 3,834,894

PROCESS FOR RECOVERING HOLYBDENUI VALUES FROM MOLYBDENITE ORE MATERIALS Filed April 10, 1969 2 SheatsSheet 2 (THE WVENT/O/V/ UPGRADED COPPER SULFIDE MOLYBDENITE FLOTATION CONCENTRATE (8.8l% Cu. 8.0l% M08 M08 CLEANER FLOTATION Nol SINK FLOAT PRIMARY HEAT TREATMENTI cOOL -wATER fi l-B FI LI E R CAKE @ANCUE ROUGHER FLOTATION] SECONDARY I-IEAT TREATMENT FLOAT SINK COOL=-FWATER L REPULP LOANCUE CLEANER FLOTATIONT GANGUE FLOTATION S NK FLOAT Q FLOAT (GANGUE C(l5EANE/R O VCENTRATE o O O.3|% RECOVEREDZ M052) M05 CLEANER FLOTATION No.2 M08 ROUGHER FLOTATION I SINK FLOAT SINK FLOAT |Mos SCAVENGER FLOTATION] MOS CLEANER I I FLOPTATION NO. 3

M08 SCAVENGER TAILING 026 Mo M SHI%%-NGCREAI\IID'IERATE A o g 2.73% RECOVERED M09 569 /0 M082 89.66% RECOVERED M03 LOW-GRADE M03 INTERMEDIATE PRODUCT TAILING H30 /0 M032 O26 2 730 RECOVERED M s 3.04% RECOVERED M082 2 CHEMICAL PROCESSING INVENTORS FOR RECOVERY OF Mo HENRY RUSH ,SPEDDEN I ARTHUR W. LAST IT RESIDUE 1, By To SMELTER COMMERCIAL FOR RECOVERY OF OTHER METAL PRODUCT flLM VALuEs ATTORNEYS United States Patent 3,834,894 PROCESS FOR RECOVERING MOLYBDENUM VALUES FROM MOLYBDENITE ORE MATE- RIALS Henry Rush Spedden and Arthur W. Last, Salt Lake City, Utah, assignors to Kennecott Copper Corporation, New York, NY.

Filed Apr. 10, 1969, Ser. No. 814,918 Int. Cl. B03d 1/00 US. Cl. 752 5 Claims ABSTRACT OF THE DISCLOSURE An improvement in the processing of molybdenite ore materials, usually molybdenite-bearing copper sulfide concentrates, for the recovery of the molybdenum values contained therein. Instead of the conventional flotation circuit, wherein middlings are recirculated and molybdenite values therein recovered in a relatively high grade molybdenite concentrate as a final product meeting established specifications as to M05 content, and normally also as to chemical grade, at least a part of the middlings are drawn off as a relatively low grade molybdenite intermediate product and are treated separately for the recovery of the contained molybdenum values. Recovery of molybdenum values in terms of both high grade concentrate and the low grade intermediate product is significantly higher than is recovery of molybdenum values in terms of the conventional high grade concentrate based on the customary recirculation of middlings.

BACKGROUND OF THE INVENTION Field The invention is in the heretofore well-developed art of froth flotation applied to the recovery of molybdenum minerals from ore materials containing same, especially copper sulfide flotation concentrates containing relatively small percentages of molybdenum sulfide predominantly in the form of molybdenite. Such concentrates are customarily subjected to reflotation procedures for the separation and recovery of the molybdenite, apart from the copper sulfides.

State of the Art It is standard practice to beneficiate low grade copper sulfide-molybdenite ores by an initial froth flotation procedure, which produces an initial or general flotation concentrate containing major proportions of both the copper sulfide and the molybdenite, and to thereafter treat this general flotation concentrate to effect a separation between the molybdenite, on the one hand, and the copper sulfides together with accompanying iron sulfides, on the other. A typical range of the pertinent metal values in the general concentrate is from approximately 25 to 38% copper and from approximately 0.6 to 1.5% molybdenum.

The molybdenite can be recovered from such a general flotation concentrate by various procedures well known to the art. The selection of any particular procedure depends upon the type of collector reagent employed to obtain the general flotation concentrate, as well as upon a variety of other factors peculiar to particular operations. Whatever the general procedure, however, it will include a reflotation operation for separating the molybdenite from the copper sulfides to produce a final, high grade molybdenite concentrate that is in accord with prevailing specifications as to MoS content (85% or above) and usually as to chemical grade as well.

The re-flotation operation as usually carried out involves both rougher and cleaner stages of flotation and 3,834,894 Patented Sept. 10, 1974 often a scavenger flotation stage utilizing the tailings from the rougher flotation. Middlings obtained from cleaner and scavenger stages of flotation are conventionally recirculated through the flotation circuit. Thus, the final, high grade molybdenite concentrate conventionally contains molybdenite from the middlings that were recirculated, but the higher the grade desired for the final product the more of the middlings that will be relegated to the final tails and the greater the loss of molybdenite.

The term middlings in this context denotes a low grade molybdenite concentrate made up of gangue minerals that were deliberately rejected and of various molybdenite mineral grains that did not respond to the initial flotation procedure, including true metallurgical middlings, i.e. mineral grains made up of both copper sulfide minerals and molybdenite, and process middlings, i.e. particles of molybdenite that, for some reason, did not float sumciently rapidly to report in the froth under the particular processing conditions.

In the handling of the conventional molybdenite flotation circuit, it is customary to recirculate the middlings for a reason additional to improved recovery of molybdenite minerals due to the increased opportunity for process middlings to report in the froth. Thus, it is customary to operate molybdenite flotation circuits with large circulating loads of minerals, i.e. to crowd the circuit, so as to limit froth residence time and thereby promote competition between the mineral species for retention by the flotation froth.

Objective To recover more of the molybdenum values from a given ore material, while producing a molybdenite concentrate conforming to established grade specifications at least so far as molybdenite content is concerned.

SUMMARY OF THE INVENTION In accordance with the invention, either part or all of the middlings from the cleaner stage or stages and/ or from any scavenger stage or stages are drawn off as a low grade molybdenite intermediate product for treatment separately from the recirculating flotation pulp.

It has been found that molybdenite middlings, as drawn off rather than being recirculated .in the customary manner, can be effectively treated independently for the re covery of molybdenum values, and that, as so drawn off and separately treated, the total recovery of molybdenum values from the operation is significantly greater than if the middlings were recirculated in the usual manner. Moreover, the increase in recovery of molybdenite from the flotation operation can be achieved economically, even though the customary crowding of the flotation circuit is greatly reduced or entirely eliminated.

There are a variety of Ways in which the withdrawn middlings can be treated for the recovery of the contained molybdenum values. Thus, in co-pending application, Ser. No. 810,449, filed by Paul B. Queneau and John D. Prater on Mar. 26, 1969, entitled Combined Chemical Treatment and Flotation Process for Recovering Relatively High Grade Molybdenite From Off Grade or Low Grade Ore Materials, and having ownership in common with the present application, there is disclosed the special processing of relatively low grade molybdenite ore materials by preconditioning such materials with a preliminary sulfuric acid or chlorine gas roast to prepare them for a subsequent froth flotation procedure to recover a molybdenite froth concentrate of commercially acceptable, specification grade from the standpoints of both M05 content and chemical purity. The roasted molybdenite ore material is subjected to aqueous leaching for the removal of solubilized impurities, and the residue of this leaching step is subjected to conventional molybdenite flotation for the recovery of a high grade molybdenite froth concentrate.

Other ways of treating the middling intermediate product drawn off from the copper sulfide-molybdenite flotation circuit in accordance with the invention include roasting of such product to convert the sulfides to their sulfates or oxides, and leaching the roasted material with sodium hydroxide for total solubilization of the molybdenum and for rejection of the copper, iron, and insoluble impurities in the residue. The solubilized molybdenum may then be recovered from the leach solution by chemical precipitation, or, following pH adjustment of such leach solution, by solvent extraction. If desired, the middling intermediate product may be leached by a basic sodium hypochlorite solution to selectively extract the molybdenum in accordance with the teachings of R. B. Bhappu, D. H. Reynolds, and W. S. Stahman in the publication Studies in Hypochlorite Leaching of Molybdenite, New Mexico Bureau of Mines and Mineral Resources, Circular 66, 1963. However, none of these other Ways known to applicants compare in effectiveness with the aforementioned Queneau-Prater process.

THE DRAWINGS In the accompanying drawings, which illustrate procedures presently contemplated as the best mode of carrying out the invention:

FIG. 1 is a flowsheet representing a conventional flotation circuit constituting prior art; and

FIG. 2, a corresponding flowsheet representing one way of carrying out the improved practice constituting the invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT For purposes of comparison, there is illustrated in FIG. 1 a conventional approach to the recovery of molybdenite from a copper sulfide-molybdenite flotation concentrate, and in FIG. 2 an approach taken in accordance with the invention. The feed material in both instances is a general flotation concentrate of copper sulfide minerals and molybdenite. The flotation circuit of FIG. 1 is typical of conventional practice at Kennecott Copper Corporations Utah Copper Division. The comparative flotation circuit of FIG. 2 represents one way the invention may be carried out in actual practice.

In the prior art process of FIG. 1, the mixed copper sulfide-molybdenite general concentrate is subjected to a preliminary heat treatment of from 500 to 540 F. for a period of thirty minutes in a roaster-dryer, followed by cooling and repulping with water. The repulped material is then subjected to rougher flotation with the usual reagents, i.e. lime and methyl isobutyl alcohol, to obtain a froth concentrate of silicious gangue (designated a float product). The remaining molybdenite values constitute a sink product. The gangue float is normally subjected to cleaner flotation with the usual reagents, i.e. dextrine and methyl isobutyl alcohol, to remove more of the molybdenite and to produce a float product to be sent to the smelter for recovery of the copper. The sink product resulting from this gangue cleaner flotation is filtered and recirculated to the primary heat treatment.

The molybdenite sink product from the gangue rougher flotation stage is subjected to molybdenite rougher flotation in the presence of the usual flotation reagents for molybdenite, i.e. lime, sodium silicate, and burner oil, to produce a float product in the form of a froth concentrate of the molybdenite values. This is sent through a cleaner flotation circuit to product the desired high-grade molybdenite concentrate. A recovery of 92.12% of the molybdenite contained in the initial feed concentrate is typical. As illustrated, such cleaner flotation circuit comprises a first cleaner flotation stage to produce a float product in the form of a molybdenite froth concentrate that is filtered, subjected to a secondary heat treatment corresponding to the previously described primary heat treatment of the initial concentrate feed material, cooled and repulped with water, and subjected to ganugue flotation with the same reagents as in the initial gangue rougher flotation to produce a sink product that is passed through a second and third stage of cleaner flotation to yield the final high-grade molybdenite concentrate.

The sink product from the first cleaner flotation stage constitutes middlings that are sent to the molybdenite rougher flotation stage along with the sink product from the gangue rougher flotation stage, while the sink products from the second and third cleaner flotation stages constitute middlings that are recirculated within the cleaner flotation circuit. The float product from the gangue flotation stage of the cleaner flotation circuit also constitutes middlings that are filtered along with the sink product from the initial gangue cleaner flotation stage and recirculated to the primary heat treatment stage.

The sink product from the molybdenite rougher flotation stage constitutes tailings so far as the present process is concerned and is passed through a molybdenite scavenger flotation stage for the recovery of a molybdenite float product, representing middlings, and the production of a sink product constituting a final copper sulfide tailing that is sent to the smelter along with the initial gangue cleaner concentrate for copper recovery.

The recovered middlings from this molybdenite scavenger flotation stage are customarily recirculated as indicated, being filtered along with other middlings from the initial gangue cleaner flotation stage and from the gangue flotation stage of the cleaner flotation circuit and returned to the primary heat treatment stage.

In the process of the present invention as illustrated by FIG. 2, these same processing steps are carried out on similar feed material, the only difference being that part of the molybdenite middlings are drawn oil as a low grade molybdenite intermediate product. Thus, in the present instance the float product from the molybdenite scavenger flotation is drawn off as a low-grade intermediate product for separate processing for the recovery of M08 rather than being recirculated through the system. As previously indicated, it has been found that total molybdenite recovery is greater by this procedure than it is by the prior art procedure of FIG. 1.

In the illustrated instance, only middlings from the molybdenite scavenger flotation stage are drawn off. It should be understood, however, that the locations from which middlings are drawn off in any metallic sulfidemolybdenite flotation circuit to which the invention is applied and the quantities drawn off from the middlings available at such locations will depend in any given instance on the economics of the system, considering especially the amount of the low grade molybdenite intermediate product that can be eflectively handled by separate processing techniques.

Results of comparative laboratory tests, which conformed to the respective flotation circuits of FIGS. 1 and 2, are shown in the following tables:

TEST A Recovery of a single high grade molybdenite concen trate in accordance with the flotation circuit of FIG. 1.

Molybdenitc percent TEST B Molybdenite percent Weight percent Assay Recovery Tailing 87. 67 0. 26 3. 04 High grade M082 concentrate 7. 40 89. 69 89. (56 Low grade M082 concentrate 4. 84 11. 3O 7. 30 Calculated feed 100.00 7. 49 100. 00

The above tests show a combined recovery of molybdenite in Test B of 96.96%, and a recovery of only 92.12% in Test A. Thus, there was a gain of 4.84 percentage points by the process of this invention.

The low grade molybdenite concentrate constituting the separate intermediate product of the present process is treated separately for the recovery of molybdenum, preferably for the production of a separate high grade molybdenite concentrate that can be combined with the initial molybdenite concentrate obtained as a high grade product. As previously indicated, this is preferably accomplished by the upgrading process set forth in the aforementioned co-pending Queneau-Prater US. application Ser. No. 810,449.

What is claimed is:

1. In a process for recovering molybdenite from ore materials containing same, wherein such an ore material is subjected to flotation treatment in a flotation circuit for the recovery of a molybdenite concentrate as a high grade product, with material being recirculated and with tailings being discharged from the circuit, the improvement comprising drawing otf as a relatively low grade intermediate product molybdenite middlings that would normally be recirculated; and subjecting said intermediate product to treatment for the recovery of the molybdenum values therein separately from the thereby reduced circulating load in the said circuit, the combined molybdenite recovery from the withdrawn middlings and from the high grade product being greater than would be obtained by retaining said withdrawn niiddlings as part of the recirculated load.

2. The improved process of Claim 1, wherein the ore material is a sulfide mineral concentrate containing molybdenite; wherein the ore material is molybdenite containing sulfide mineral concentrate is subjected to a preliminary treatment to deactivate the molybdenite minerals prior to flotation; wherein the so-treated concentrate is subjected to rougher flotation in which molybdenite minerals are depressed and concentrated in a sink product; and wherein the said sink product is subjected to cleaner flotation for the recovery of the molybdenite minerals in a float product.

3. The improved process of Claim 1, wherein the separate treatment for the intermediate product comprises upgrading the middlings by a combination of chemical and flotation treatment to a grade approximately equivalent to the high grade molybdenite concentrate.

4. An improved process in accordance with Claim 1, wherein treatment of the molybdenite middlings, as the intermediate product drawn off, is by procedures other than mechanical sizing for the recovery of the molybdenite values contained therein.

5. An improved process in accordance with Claim 4, wherein the treatment of the withdrawn molybdenite middlings is by chemical processing procedures.

References Cited UNITED STATES PATENTS 2,716,600 8/1955 Prick et a1. -2 3,117,860 1/1964 Bjerkerud et al. 75-121 X 3,357,821 12/1967 Henrickson 75-121 X 3,386,572 6/1968 Cadwell 75-2 X 3,455,677 7/1969 Litz 75121 X FOREIGN PATENTS 864,529 4/1961 Great Britain 75--2 208,400 5/1967 Australia 75-1 ALLEN B. CURTIS, Primary Examiner 

